Seal with flexible nose for use with a lock-down ring on a hanger in a wellbore

ABSTRACT

A seal system selectively set between coaxial downhole tubulars seals between the tubulars; the system also locks the tubulars together to resist relative axial movement from thermal expansion. The seal system includes a seal element with a nose ring that couples a lock-down ring to both the inner and outer tubulars. Before inserting the seal system between the tubulars, the lock-down ring is disposed in a groove on the inner tubular. Setting the seal system drives a lower tip of the nose ring between the lock-down ring and inner tubular, thereby urging the lock-down ring radially outward. A portion of the lock-down ring remains in the groove, while an outer radial portion of the lock-down ring inserts into a profile on the outer tubular. Axial movement of a tubular transfers force to the other tubular through the lock-down ring, while a minimal amount of force transfers through the seal system.

BACKGROUND

1. Field of Invention

The present disclosure relates in general to wellhead assemblies, and inparticular to a seal and lock-down ring for use between inner and outerwellhead members.

2. Description of Prior Art

Seals are typically provided in an annulus between coaxial wellheadtubular members to isolate internal well pressure. The inner wellheadmember is sometimes a tubing hanger that supports a string of tubingextending into the well for the flow of production fluid. The tubinghanger lands in an outer wellhead member, which may be wellhead housing,a production tree, or tubing head. A packoff or seal typically forms abarrier between the tubing hanger and the outer wellhead member. Inother times, the inner wellhead member is a casing hanger landed in awellhead housing and that has a string of casing that depends down intothe well. A seal or packoff usually seals between the casing hanger andthe wellhead housing.

The seals may be set by a running tool, or they may be set in responseto the weight of the string of casing or tubing. One type of seal hasinner and outer legs separated by a slot; in which an energizing ring isinserted that deforms the inner and outer legs apart into sealingengagement with the inner and outer wellhead members. The energizingring is usually a solid member. The seals with inner and outer legstypically plastically deform when pushed into sealing engagement withthe inner and outer wellhead members.

SUMMARY OF THE INVENTION

Disclosed herein is a seal and lock-down system for use between downholeinner and outer tubulars. In an example the system includes a sealelement having a body and inner and outer annular legs projecting fromthe body that are spaced radially apart to define a gap between thelegs, a lock-down ring between the tubulars, and a nose ring on an endof the body of the seal element distal from the legs. In this examplethe nose ring is elongate and generally parallel with an axis of thetubulars. The nose ring is selectively changeable to a set configurationthat is generally oblique with the axis when inserted between thelock-down ring and inner tubular. In one example, when the nose ring isinserted between the lock-down ring and inner tubular, the nose ringsubstantially occupies the space between the lock-down ring and innertubular. In an alternate embodiment, when the nose ring is insertedbetween the lock-down ring and inner tubular, an outer radial portion ofthe lock-down ring projects into a profile in the outer tubular and aninner radial portion is disposed in a lock-down groove on the innertubular thereby axially affixing together the inner and outer tubulars.Slots may be included that extend through sidewalls of the nose ringfrom an end of the nose ring distal from the seal element; and whereinfingers can be defined between adjacent slots. In an example embodiment,the inner radius of the lock-down ring projects radially inwardproximate a side of the lock-down ring distal from the seal element. Theouter tubular can be a wellhead housing that is part of a wellheadassembly, and the inner tubular can be a casing hanger. In one example,directing the energizing ring against the seal element with anenergizing force that urges the nose ring between the lock-ring and theinner tubular, wherein inserting the energizing ring into the gapbetween the inner and outer legs with an energizing force to theenergizing ring, drives the energizing ring into the gap and urges thelegs radially outward into sealing contact with the tubulars, andwherein the energizing force for the seal element is greater than theenergizing force for the lock-ring.

Also disclosed herein is a seal system for sealing between coaxialtubulars, where the tubulars are part of a wellhead assembly. In anexample, the seal system includes an annular seal element havingradially spaced apart inner and outer legs that define a gaptherebetween, and that are in sealing contact with opposing surfaces ofthe tubulars. The seal system further includes a lock-down ring havingopposing radial portions in interfering contact with oppositely facingprofiles in the tubulars, so that portions of the tubulars adjacent theseal element are axially static, and a nose ring. In this embodiment,the nose ring has an end coupled with an end of the seal element, and aportion spaced from the seal element is wedged between the lock-downring and one of the tubulars. When wedged as such, the nose ringprojects along a path generally oblique to the seal element, and therebyretaining the lock-down ring in interfering contact with the tubulars.The one of the tubulars can be a casing hanger; in this example theportion of the nose ring projects radially inward. A notch can be scoredon a radial surface of the nose ring so the nose ring can be changedfrom an elongate shape to the oblique shape when inserted between thelock-ring and the one of the tubulars. The nose ring can change from anelongate shape to the oblique shape when inserted between the lock-ringand the one of the tubulars, and wherein a force for inserting the nosering between the lock-ring and the one of the tubulars is less than aforce for energizing the seal element. The tubulars can be made up of aninner tubular and an outer tubular with oppositely facing profiles thatinclude an upward facing pedestal defined by a lower surface of alock-down groove formed along an outer circumference of the innertubular. The outer tubular can have a downward facing shoulder definedby a profile formed along its inner circumference.

Further described herein is a system for sealing between tubulars in awellhead assembly. In an example the system includes a seal element thatis selectively inserted between the tubulars, and a lock-down ringselectively disposed on an profile on an outer surface of a one of thetubulars. The lock-down ring can be selectively urged to a positiontowards another one of the tubulars and into interfering contact with anoppositely facing profile on the another one of the tubulars. Furtherincluded in this example is a nose ring on an end of the seal elementthat selectively inserts between the lock-down ring and the one of thetubulars into a setting position to urge the lock-down ring into theinterfering contact, so that forces resulting from relative axialmovement of the tubulars are applied to the lock-down ring and bypassthe seal element. In an example, the interfering contact of thelock-down ring maintains the portions of the tubulars adjacent the sealin relative static positions. Optionally, when the nose ring is in thesetting position the nose ring substantially occupies the space betweenthe lock-ring and the one of the tubulars. In an example, the one of thetubulars is a casing hanger and the another one of the tubulars is awellhead housing.

BRIEF DESCRIPTION OF DRAWINGS

Some of the features and benefits of the present invention having beenstated, others will become apparent as the description proceeds whentaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side sectional view of an example of a seal system beinginserted between a pair of downhole tubulars in accordance with anembodiment of the present invention.

FIG. 2 is a side sectional view of the seal system of FIG. 1 being setand energized into a sealing and lock-down configuration in accordancewith an embodiment of the present invention.

FIG. 3 is a side perspective view of an example of nose ring from theseal system of FIG. 1 in accordance with an embodiment of the presentinvention.

FIG. 4 is a side partial sectional view of an embodiment of the sealsystem and tubulars of FIG. 1 in a wellhead assembly in accordance withan embodiment of the present invention.

FIG. 5 is a plan view of an example of a lock-down ring from the sealsystem of FIG. 1 in accordance with an embodiment of the presentinvention.

While the invention will be described in connection with the preferredembodiments, it will be understood that it is not intended to limit theinvention to that embodiment. On the contrary, it is intended to coverall alternatives, modifications, and equivalents, as may be includedwithin the spirit and scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF INVENTION

The method and system of the present disclosure will now be describedmore fully hereinafter with reference to the accompanying drawings inwhich embodiments are shown. The method and system of the presentdisclosure may be in many different forms and should not be construed aslimited to the illustrated embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey its scope to those skilled in the art.Like numbers refer to like elements throughout.

It is to be further understood that the scope of the present disclosureis not limited to the exact details of construction, operation, exactmaterials, or embodiments shown and described, as modifications andequivalents will be apparent to one skilled in the art. In the drawingsand specification, there have been disclosed illustrative embodimentsand, although specific terms are employed, they are used in a genericand descriptive sense only and not for the purpose of limitation.

Shown in a sectional view FIG. 1 is one example of a portion of awellhead assembly 10 that includes a pair of coaxial tubulars 12, 14. Inthe example, tubular 14 is an inner tubular and proximate an axis A_(x)of the wellhead assembly 10. Further in the example, tubular 12 is anouter tubular which circumscribes tubular 14. Examples exist, wheretubular 12 is a wellhead housing, and tubular 14 is a casing hanger.Optionally, tubular 14 may also be a tubing hanger, wherein tubular 12may be a casing hanger. A seal assembly 16 is shown being inserted intoan annulus 18 formed between the tubulars 12, 14. The seal assembly 16includes a seal element 19 shown having an elongate outer leg 20oriented substantially parallel with axis A_(x). Seal element 19 furtherincludes an inner leg 24, which like outer leg 20 is elongate andprojects along a path generally parallel with axis A_(x). Between legs20, 24 an annular gap 26 is defined that is elongate in an axialdirection. Optional wickers 30, 31 are formed respectively on portionsof the outer and inner surfaces 28, 22. Seal element 19 further includesa body 31 on which the legs 20, 24 mount; and the body 31 defines abottom of the gap 26.

Shown threadingly mounted to an end of the body 31 opposite from legs20, 24 is an annular nose ring 32 that is elongate in an axial directionand depends from body 31 deeper into the annulus 18. Other means formounting the nose ring 32 to the body 31 may be employed, such as aC-ring (not shown) and/or threaded fasteners. A lock-down groove 34 isillustrated circumscribing the inner tubular 14 formed into the outersurface 28, and spaced downward from nose ring 32. A wall of thelock-down groove 34 that is distal from an opening of the annulus 18,projects radially outward to define a pedestal 36. In the example ofFIG. 1, the pedestal 36 provides a support ledge on the tubular 14 shownsupporting a lock-down ring 38. An example embodiment of the lock-downring 38 extends substantially the length of the lock-down groove 34,such as a “C” ring. In the example of FIG. 1, the radial section of thelock-down ring 38 has an outer surface substantially parallel with axisA_(x). While a portion of the inner surface of the lock-down ring 38proximate pedestal 36 is substantially parallel with axis A_(x), theinner surface tapers radially outward with distance away from pedestal36. The angle of the taper changes to define a transition 39, whereangle of the taper between the transition 39 and the pedestal 36 is moreoblique to axis A_(x) than the angle of the taper between transition 39and the end of the lock-down ring 38 distal from pedestal 36.Optionally, the lock-down ring 38 can fully circumscribe lock-downgroove 34. Further illustrated in FIG. 1 is a profile on the innersurface 22 of tubular 12 that projects radially inward to define ashoulder 40, wherein shoulder 40 is opposite from and faces pedestal 36.

FIG. 2 illustrates a side sectional view of the seal assembly 16 beinginserted deeper within the annulus 18 and wherein outer and inner radialsurfaces of the legs 20, 24 are in respective sealing engagement withthe inner and outer surfaces 22, 28. Further, an energizing ring 42which is inserted into the gap 26 provides a radial force for sealinglyengaging legs 20, 24 with inner and outer surfaces 20, 28. An axialforce F applied to energizing ring 42 further downwardly urges the sealelement 19 and nose ring 32 so that nose ring 32 is in contact withlock-down ring 38. In this example, nose ring 32 is shown having aflexible portion that deforms when wedged between lock-down ring 38 andinner groove 34 in inner tubular 14. When deformed, nose ring 32 is in aconfiguration generally oblique to the axis A_(x), which is in contrastto the elongate configuration of FIG. 1 that is generally parallel withaxis A_(x). Lock-down ring 38 is shown being urged radially outward atleast partially out of lock-down groove 34 and into interfering contactwith tubular 12 while remaining in interfering contact with tubular 14.More specifically, a surface of lock-down ring 38 distal from sealelement 19 rests on and is in contact with the pedestal 36 of tubular14. Urging the lock-down ring 38 radially outward in the example of FIG.2, further positions a surface of lock-down ring 38 proximate sealelement 19 into engaging contact with shoulder 40. As such, relativeaxial movement between tubulars 12, 14 is arrested by the presence ofthe interfering lock-down ring 38. Additionally, substantially all axialforces resulting from respective axial movements of the tubulars 12, 14are transferred through the lock-down ring 38. Thus, forces on the sealelement 19 that result from forces that transfer between the tubulars12, 14, can be minimized. The compound angle created by the transition39 on the lock-down ring 38 also reduces relative movement between theseal assembly 16 and the inner tubular 14. The more oblique surfacebetween the transition 39 and pedestal 36 urges the lower terminalportion of the nose ring 32 radially inward, where it is wedged betweenthe lock-down ring 38 and outer surface 28 of inner tubular 14.Strategically profiling the inner surface of the lock-down ring 38 andouter surface 28, in combination with the flexible nose ring 32, directsforces from the lock-ring 38 to the nose ring 32 in a direction obliqueto the axis A_(x), instead of parallel to the axis A_(x). Obliquelydirecting forces from the lock-ring 38 to the nose ring 32, rather thandirecting the forces axially, creates a force coupling the nose ring 32,and attached seal assembly 16, to the inner tubular 14, As such, duringepisodes of thermal expansion of the casing or casing hanger, sealintegrity may be maintained between tubulars 12, 14 by bypassing theresulting axial forces through lock-down ring 38. Bending of the nosering 32 may be facilitated by scoring an inner radial surface oflock-down ring 38 with a notch 43, wherein notch 43 may extend along anentire circumference of nose ring 32 or along a portion thereof.

Referring now to FIG. 3, shown in perspective view is an alternateembodiment of nose ring 32A, that includes axial slots 44 that extendfrom an end of the nose ring 32A distal from its attachment with sealelement 19 into a mid-portion of the body of nose ring 32A. The slots 44can each have the same length, or as have different lengths as shown.Positioning of the slots 44 define elongate fingers 46 between adjacentslots 44, where the absence of material due to slots 44 reduces theforce required for deforming sidewalls of the nose ring 32A, therebyfacilitating its deformed setting position as illustrated in FIG. 2. Inan example, the axial force required for positioning the nose ring 32,32A into the setting position illustrated in FIG. 2 is less than theaxial force required for energizing the seal element 19. In thisexample, the nose ring 32 would be in the set position of FIG. 2 andbetween the lock-down ring 38 and inner tubular 14 before the energizingring 42 would set the legs 20, 24 into sealing contact with the innerand outer tubulars 14, 12.

FIG. 4 provides a side partial sectional view one example of the sealassembly 16 set between tubulars 12, 14. The tubulars 12, 14 are part ofthe wellhead assembly 10, which is shown mounted on a surface 48 of aformation through which a wellbore 50 is formed. Casing 52 dependsdownward from tubular 14, and a production tree 54 is shown mounted ontubular 12. A main bore 56 extends through wellhead assembly 10 and intocommunication with wellbore 50, wherein a swab valve 58 is disposed inmain bore 56 for controlling access into the wellbore 50. Also, wingvalves 60 are shown set in lines that mount to the production tree 54.

Shown in a plan view in FIG. 5 is an alternate embodiment of lock-downring 38A and shown having slots 62 formed axially from an outer terminalradius of lock-down ring 38A approximately to a mid-portion of the bodyof the lock-down ring 38A. In this example, slots 64 are formed axiallythrough lock-down ring 38A from its inner diameter that extend radiallyoutward approximately to a mid-portion of the body of lock-down ring38A. In the example of FIG. 5, slots 62 are offset from slots 64,however, alternate embodiments exist where slots 62, 64 are aligned orspaced apart at different angular locations than as shown.

The present invention described herein, therefore, is well adapted tocarry out the objects and attain the ends and advantages mentioned, aswell as others inherent therein. While a presently preferred embodimentof the invention has been given for purposes of disclosure, numerouschanges exist in the details of procedures for accomplishing the desiredresults. These and other similar modifications will readily suggestthemselves to those skilled in the art, and are intended to beencompassed within the spirit of the present invention disclosed hereinand the scope of the appended claims.

What is claimed is:
 1. A seal system for use between downhole inner andouter tubulars comprising: a seal element having a body and inner andouter annular legs projecting from the body that are spaced radiallyapart to define a gap between the legs; a lock-down ring between thetubulars; and a nose ring on an end of the body of the seal elementdistal from the legs that has an elongate side having an insertingconfiguration that is generally parallel with an axis of the tubulars,and selectively changeable to a set configuration that is generallyoblique with the axis when inserted between the lock-down ring and innertubular.
 2. The seal system of claim 1, wherein when the nose ring isinserted between the lock-down ring and inner tubular, the nose ringsubstantially occupies the space between the lock-down ring and innertubular.
 3. The seal system of claim 1, wherein when the nose ring isinserted between the lock-down ring and inner tubular, an outer radialportion of the lock-down ring projects into a profile in the outertubular and an inner radial portion is disposed in a lock-down groove onthe inner tubular thereby axially affixing together the inner and outertubulars.
 4. The seal system of claim 1, further comprising slots thatextend through sidewalls of the nose ring from an end of the nose ringdistal from the seal element.
 5. The seal system of claim 4, whereinfingers are defined between adjacent slots.
 6. The seal system of claim1, wherein the inner radius of the lock-down ring projects radiallyinward proximate a side of the lock-down ring distal from the sealelement.
 7. The seal system of claim 1, wherein the outer tubularcomprises a wellhead housing that is part of a wellhead assembly, andwherein the inner tubular comprises a casing hanger.
 8. The seal systemof claim 1, wherein directing the energizing ring against the sealelement with a nose ring energizing force urges the nose ring betweenthe lock-ring and the inner tubular, wherein inserting the energizingring into the gap between the inner and outer legs with a sealenergizing force on the energizing ring, drives the energizing ring intothe gap and urges the legs radially outward into sealing contact withthe tubulars, and wherein the seal energizing force is greater than thenose ring energizing force.
 9. A seal system for sealing between coaxialtubulars that are part of a wellhead assembly comprising: an annularseal element having radially spaced apart inner and outer legs thatdefine a gap therebetween, and that are in sealing contact with opposingsurfaces of the tubulars; a lock-down ring having opposing radialportions in interfering contact with oppositely facing profiles in thetubulars, so that portions of the tubulars adjacent the seal element areaxially static; and a nose ring having an end coupled with an end of theseal element and a portion spaced from the seal element that is wedgedbetween the lock-down ring and one of the tubulars and projects along apath generally oblique to the seal element, and thereby retaining thelock-down ring in interfering contact with the tubulars.
 10. The sealsystem of claim 9, wherein the one of the tubulars comprises a casinghanger, and wherein the portion of the nose ring projects radiallyinward.
 11. The seal system of claim 9, wherein a notch is scored on aradial surface of the nose ring so the nose ring can be changed from anelongate shape to the oblique shape when inserted between the lock-ringand the one of the tubulars.
 12. The seal system of claim 9, wherein thenose ring changes from an elongate shape to the oblique shape wheninserted between the lock-ring and the one of the tubulars, and whereina force for inserting the nose ring between the lock-ring and the one ofthe tubulars is less than a force for energizing the seal element. 13.The seal system of claim 9, wherein the tubulars comprise an innertubular and an outer tubular, and oppositely facing profiles in thetubulars comprise an upward facing pedestal defined by a lower surfaceof a lock-down groove formed along an outer circumference of the innertubular and a downward facing shoulder defined by a profile formed alongan inner circumference of the outer tubular.
 14. A system for sealingbetween tubulars in a wellhead assembly comprising: a seal elementselectively inserted between the tubulars; a lock-down ring selectivelydisposed on an profile on an outer surface of a one of the tubulars, andselectively urged to a position towards another one of the tubulars andinto interfering contact with an oppositely facing profile on theanother one of the tubulars; and a nose ring on an end of the sealelement that selectively inserts between the lock-down ring and the oneof the tubulars into a setting position to urge the lock-down ring intothe interfering contact, so that forces resulting from relative axialmovement of the tubulars are applied to the lock-down ring and bypassthe seal element.
 15. The system of claim 14, wherein the interferingcontact of the lock-down ring maintains the portions of the tubularsadjacent the seal in relative static positions.
 16. The system of claim14, wherein when the nose ring is in the setting position the nose ringsubstantially occupies the space between the lock-ring and the one ofthe tubulars.
 17. The system of claim 14, wherein the one of thetubulars comprises a casing hanger and the another one of the tubularscomprises a wellhead housing.